Immense quantities of waste materials have accumulated at Federal laboratories throughout the United States, and in other countries as well, as a result of the large amount of nuclear research in preparation of fissionable materials for atomic bombs including for use during World War II; in improvement of efficiency and recovery techniques of fissionable materials and fission fragments; and in development of uses for radioactive elements in industry, medicine, and commercial use. In many cases, the equipment used in handling these materials has been contaminated. Safety equipment used to prevent exposure of personnel to the radiation has also been contaminated. Because of this contamination, all of this equipment has been discarded. This, despite that fact that the actual contamination level is extremely low. As a result of this situation, in many cases tons of material have been discarded which has been contaminated with a few microcuries of radioactivity.
The ultimate result of all this is that there are literally millions of cubic yards of slightly contaminated materials which must be treated in order to reduce the sheer volume of material which must be stored in a permanent repository.
In addition to these slightly contaminated waste materials, there are also huge volumes of liquids and solids which may include some chemicals which are hazardous to human health, which may contain small or large quantities of radioactive materials. These may consist of animals which have been injected with radioactive chemicals; solutions of radioactive species used in experiments; mill tailings from radioactive ore beneficiation; tagged chemicals, and many others.
The entire problem is exacerbated by the fact that many of these materials were mixed indiscriminately when they were discharged, so that now there is no convenient way to separate the merely hazardous or radioactive from the non-hazardous or non-radioactive waste.
The present invention relates generally to a method of and system for reducing the gross volume of these contaminated wastes by exposing them to the surface of molten metallic aluminum. This metal can be pure aluminum metal, alloys, or eutectic mixtures of other metals which may be either more or less reactive than the aluminum. Such metals may include sodium, potassium, calcium, magnesium, lead, iron, zinc, copper, etc.
A number of successful approaches have been proposed by applicant for treating waste products. Some of these approaches are described in U.S. Pat. Nos.: 4,469,661; 4,552,667; 4,559,141; 4,666,696; and 4,695,447 and relate to the destruction of a variety of waste products, including biological waste products; hazardous waste containing organic compounds having covalently bound oxygen, nitrogen, sulfur or phosphorus; inorganic compounds which contain heavy metals or particular hazardous anionic groups or which are hazardous nonmetal oxides or sulfides; pathological materials; and hazardous halogenated hydrocarbon non-radioactive materials.
For instance, U.S. Pat. No. 4,469,661, describes a system for treating solids contaminated with polychlorinated biphenyl (PCB) and other hazardous halogenated hydrocarbons which are reacted with molten aluminum. Because of this reaction, chlorine will be abstracted from the organic materials, since aluminum chloride is formed which is a volatile salt that may be distilled from the reaction mixture. In this patented process, there is a direct reaction of the liquid PCB; the passage of PCB-contaminated oils or solvents through the reactor so that the PCBs react, and the oils are distilled from or carbonized in the reactor; or the extraction of PCBs from soil or other contaminated materials with a suitable high-boiling hydrocarbon solvent and subsequent passage through the reactor.
Still another approach is set forth in the U.S. Pat. No. 4,552,667 which patent describes a system for disposing of both liquid and solid hazardous wastes of the type including organic compounds which contain covalently bound oxygen, nitrogen, sulfur and/or phosphorus. In this approach, both liquid and solid hazardous wastes are pumped from a tank through a vat of molten aluminum wherein reacting vapors rise from the reaction zone into a water trap arrangement.
While these approaches are successful, there is nevertheless a continuing desire to improve upon their applicability and performance, especially from the standpoint of handling radioactivity. For instance, there is a continuing desire to economically reduce the volumetric amounts of waste materials generated at nuclear industrial or research sites; these wastes contain mixtures of various waste materials some of which are hazardous by reason of their radioactivity and others are hazardous by virtue of their nature. Such wastes include, for example, the radio-nuclides on wiping tissues which are saturated with chlorinated solvents; others are inorganic nuclides in the presence of solvents; some are radioactively labeled compounds. It will be appreciated that the volume of such wastes increases daily as research and nuclear power generation activities continue. Given the excessive damages that can arise from accidental discharge of pollutants, it can be extremely expensive to safely and legally dispose of such wastes. To minimize pollution problems, these hazardous and radioactive wastes must be treated and disposed of in accordance with stringent guidelines.
Prior efforts have not provided an entirely satisfactory and economical approach to reducing the volume of mixtures of wastes. For instance, at nuclear sites, the radioactive wastes are and have been stored in special containers and it is possible that such containers can include a variety of contaminants (including PCBs) in addition to radioactive contaminants. In order to safely dispose of the contents of such containers, especially older containers, an analysis of each is usually undertaken. The costs of such inspections can be extremely expensive--if not prohibitive--considering the large quantities of these containers which must be tested for proper disposal.